Drawing FIG. 1 schematically represents a top plan view of a pair of substantially identical conventional railroad locomotives 100 respectively extending along a common longitudinal-axis 99 and wherein the flanged wheels (W) rest upon track rails 97 and 98 flanking axis 99. In FIG. 1, portions of the locomotive roof are cutaway to expose an upright barrier-partition 100A as the rearward terminus of operator's cab 103 extending toward locomotive forwardend 101 and also as the forward terminus of a power-source compartment 104 extending toward locomotive rearward-end 102. Positioned within compartment 104 is a diesel engine 110 which drives a main-generator 111, the rectified (D.C.) high-voltage electricity therefrom causing traction motors (not shown) to drive the wheels (W) and through the intervention of conventional controls. Such controls are schematically indicated as two levers mounted to a controller-assembly located within cab 103, namely: reverser lever 105 which functions as a forward(105F)-rearward(105R) motive directional control; and throttle lever 106 which functions as acceleration control. Also positioned within power-source compartment 104 is an auxiliary generator 113, the rectified (D.C.) low-voltage electricity therefrom being actuatably connected to appropriate components such as: controls 105 and 106, the exciter field 112 for main-generator 111, audible alarm 107 etc. Other salient features of FIG. 1 include operator's ingress-egress door 109 to compartment 103, transparent windshields (Y), an externally mounted hanger 108, and an alarm device (e.g. audible bell 107) discernable internally and externally of cab 103. Within power-source compartment 104 is one or more valves (e.g. 114) which governs the amount of fuel reaching the diesel engine 110. In a related vein, main-generator 111 requires less fuel and a lower r.p.m. when the locomotive is stopped and the wheels' traction motors have no demand for high-voltage electricity.
Reference characters 120 of FIGS. 1 and 2 are the two multi-pins receptacle terminii of said low-voltage (e.g. 74 volts) electrical circuitry emanating from auxiliary generator 113 and which extends the longitudinal length of each locomotive (100). Individual pins of the multi-pins terminal units 120 are conventionally consecutively numbered from "1" to "27" and are electrically connected to the appropriate low-voltage locomotive component such as, inter alia:
"2" to the discernible alarm (e.g. audible bell 107), PA1 "3" to the speed control (e.g. 106 via 114), PA1 "4" to the negative or "ground" of the auxiliary generator (e.g. 113N), PA1 "6" to the exciter circuit (e.g. 112) for the main generator (111), PA1 "8" to the directional control (Forward) (e.g. 105F), PA1 "9" to the directional control (Rearward) (e.g. 105R), PA1 "13" to the low-voltage power of the auxiliary generator (e.g. 113P), PA1 etc.
A conventional two-headed jumper 119, having a plurality of orifices at each head corresponding to the number of pins for the "MU" unit 120, may be conventionally employed to removably electrically connect adjacent locomotives to provide a "consist" of coacting locomotives.
Once the operator has brought the locomotive to a lengthy stop within the railyard and departs from the cab (103), the locomotive becomes a candidate for servicing by railyard maintenance personnel. At this stopped condition, the forward-rearward directional control (105) is in "neutral"; moreover, the acceleration control (106) is at "idle" setting whereby by virtue of unit pins "3" and "6", the continuously running diesel engine 110 is maintained at low r.p.m. whereby no high-voltage D.C. electricity is generated for the wheels (W) traction motors. However, the diesel engine 110 at such low r.p.m. condition is sufficient for generating the low-voltage D.C. electricity for all the "MU" unit (120) circuitry and its "1" to "27" pins.
Inasmuch as such railyard maintenance personnel must oftentimes position themselves adjacent to the wheels (W) or other perilous servicing location, it is imperative that no one within cab 103 be permitted to initiate longitudinal movement of the locomotive. In the latter regard, the locomotive is said to be classified in a dangerous "blue flag" condition as is defined, inter alia, by 49 C.F.R. sections 218.21-218.29. In the prior art, a hooked pole equipped with a blue-colored flag is hung (e.g. at 108) and intended to be viewable through windows (Y) as a warning to cab personnel to refrain from attempting to initiate longitudinal movement to the stopped locomotive. Unfortunately, however, such blue-colored flags are sometimes improperly positioned or cannot be seen through frosted or otherwise obstructed windows whereby the cab personnel are not actually notified of the perilous "blue flag" condition. Unfortunately also, and because of fatigue or other human error, cab personnel unintentionally fail to notice or to heed the hung blue-colored flag.